Frame rebuild metal choice

[CajunCan]

Hello all, I am looking for some advice on my selection of steel for constructing a new frame.

I will be rebuilding the frame for my 31' 1976 sovereign from scratch since the existing frame is bent and in to bad of shape to repair. I am however going to use the existing A-frame since it is in perfect shape.

I will be using 5x2 rectangular tubing for the main rails and cross members. I have a choice to use either 3/16 thick metal or 1/8 tubing.

There is not much of a price difference. All of the metal will cost me about $ 700 - $ 800 depending on which way I go.

The weight difference is (1/8 =5.5 pounds per foot) and (3/16 = 8.75 pounds per foot).

What are your opinions on my thickness options?

[57Vintage]

My thought would be the 3/16" for the main frame rail. 1/8" for the internal crossmembers with 3/16" for the front and rear crossmembers.

What are you thinking about on the outriggers?

[DGJackson]

I used 2x5 1/8" box when I replaced the frame on my '73 25-ft. This was for frame rails and cross pieces. I used 3/16 for the A-Frame. The local steel supplier precision cut the angles on the A-Frame with a very cool digital bad saw having 20-ft feed and runout table. I think my coupler was 52-degree. I used replacement outriggers from Out-of-Doors mart in NC.

If the frame is anything like my '73 25-ft you are replacing what I believe is shear bent 11-gauge C-channel with extruded 2x5 box. The bending moment for box cross-section is much stronger than C-channel. That's why old hot rodders and street racers box frames on cars. On the rear of my frame from axles to bumper there was a "cripple joist/2X3" c-channel" welded to the underside essentially creating an "E-Cross Section". I determined the box structure was equivalent or better - I have a mechanical engineering background.

If I had it to do over I would have reduced some weight and cut cross-pieces in half (1x5 C-channel) and cut 4" circles to removed mass on crossbars. Similar to what you can buy at Out-of-Dorrs mart. Live and learn.

Don't overbuild your frame. When you select axles you want the axles to be sized for the gross weight - there are lots of discussions on that aspect. Also want some flexibility in frame - a lot of opinions on that topic.

Just my approach and what I would consider if I do it again.

Dennis

[Indy_Air]

Dennis, was the second C channel in the back to create depth for the black tank or purely structural? (if you had a rear bath) I'm sure you get way more clearance by going with just a box frame.


Remember when installing your axles on the frame to square from the front-center of the ball hitch. That way you're not pulling from an end that might not be perfectly square or the exact length.



Shane

[CajunCan]

I believe I will most likely go with the 5x2x1/8 box for the main frame rails, cross members, and out riggers. As I said before, my A frame hitch is in good shape so I am going to try to cut it out and reuse it. I will also run a 2x2x3/16 square tube that is 10 feet long on each side of the main rails on the underside where the axles mount in the middle section. The added 2x2 will give me 7 inches of total space to put grey/black tanks while also adding some lift to the frame without much weight added.

My frame sounds identical to what Dennis said about his. I do not think that the c channel on the rear of the frame is structural except for mounting the grey and black water tank in the rear for rear bathrooms. I will be moving my bathroom to the center so I am doing away with the tank mounts in the rear which will also give me more clearance in the back. For my cross members I plan to cut holes in the box like the existing cross members have to reduce some weight.

[tbashin]

More is better. 3/16"

[glrtex]

CajunCan,
Is your ‘76 a rear or center bath? I might to able to save you time and money.
I built a frame for my ‘76 31’ Sovereign last year. I had brand new Dexter axles and new Goodyear tires. I posted it in the Classified section. I used 2x6 tubing and it has two coats of POR-15. While separated, the shell was the victim of a wind storm that destroyed it ending my project.
The only gotcha is that you would have to have custom banana wraps made, which any good body man with an English wheel could make.
Let me know if you are interested. I can forward photos and a dimensioned drawing.

Greg